In subsea drilling operations using a surface vessel, it is highly desirable to keep the vertical axis of the drilling pipe or riser, at a working deck elevation, in line with the vertical axis of the rotary table. This is usually accomplished by providing an opening in the working deck and the use of a centralizer for centering the riser in the opening.
Examples of prior art devices disclosing such centralizers and related equipment are found in the following U.S. Pat. Nos. 920,548 to Decker; 2,631,822 to Ussery; 2,661,189 to Gillerstrom; 2,906,799 to Schlienger; 3,053,022 to Mercier; 3,142,343 to Otteman; 3,206,259 to Curtis; 3,313,358 to Postlewaite et al; 3,334,606 to Deal; and 3,884,298 to Watkins.
Unfortunately, these prior art assemblies have numerous disadvantages such as being complicated and costly to manufacture. In addition, they cannot be easily assembled and disassembled for relocation at subsequent well locations. Thus, there is a continuing need for improvement in such centralizers.